1. Field of the Invention
The present invention relates to a digital video receiver, a conditional access module and a method of transferring data therebetween. In particular, it relates to systems allowing higher rates of flow for the control data.
2. Description of the Related Art
As illustrated in FIG. 1 of the accompanying drawings, it has been proposed to provide a digital video broadcasting (DVB) receiver 2 in conjunction with a conditional access sub-system (CASS) 4. The CASS module 4 controls access to a broadcast service, for instance by descrambling a transmitted broadcast. The CASS module 4 may also hold service entitlement information, controlled by the service provider. The service provider may communicate with the CASS module 4 using encrypted messages carrying descrambler keys and service management information.
In order for the CASS module 4 to descramble a transport stream, such as an MPEG transport stream, received by the DVB receiver 2, an interface is provided between the DVB receiver and the CASS module. The interface has a plurality of lines 6 allowing the transport stream to be sent to the CASS module 4 and a plurality of lines 8 allowing the transport stream to be sent back to the DVB receiver 2.
As illustrated, it, is also proposed that a command interface 10 should be provided between the DVB receiver 2 and CASS module 4. The command interface 10 allows communication between the DVB receiver 2 and CASS module 4 with regard to functioning of the DVB receiver 2 and CASS module 4.
The command interface 10 is preferably a polled (with an option for interrupts) byte wide connection. The DVB receiver 2 detects if the module 4 has data to send and then reads it back a byte at a time from the module 4 and, if the DVB receiver 2 has data to send, it checks that its buffer is free and then sends the data a byte at a time to the module 4.
Thus, the interface operates by sending packets of a fixed maximum size across the interface 10. The maximum size of these packets is governed by the buffer size of the DVB receiver 2 or module 4, the DVB receiver 2 reading the module buffer size as part of the interface initialization.
Thus, the maximum bit rate capacity of the command interface 10 is relatively small.
It is proposed that the CASS module 4 could be used for functions other than merely descrambling the transport stream. For example, the CASS module 4 could be used in an interactive way, communicating with the remote control of the DVB receiver 2, communicating with a modem in the DVB receiver 2 or producing relatively complicated graphics for display on the television screen. For these functions, the command interface data rates impose a limitation, for instance creating undesirable delays in operation and jerky movement on screen.
It is an object of the present invention at least to educe these problems.
According to the present invention, there is provided a method of operating a digital video receiver having a multi line socket for connection to a conditional access module, the socket having a predetermined plurality of lines for transmitting and receiving transport stream data and a predetermined plurality of lines for transmitting and receiving control data and resource/application data, the method comprising:
selectively transmitting resource/application data over the plurality of transport stream lines.
There is also provided a digital video receiver including:
a multi line socket for connection to a conditional access module, the socket having a predetermined plurality of lines for transmitting and receiving transport stream data and a predetermined plurality of command lines for transmitting and receiving control data and resource/application data, wherein
the receiver is arranged to selectively transmit and receive resource/application data over the plurality of transport stream lines.
There is also provided a conditional access module for connection to a multi line socket of a digital video receiver, the module including:
a predetermined plurality of lines for transmitting and receiving transport stream data to and from corresponding lines of the socket; and
a predetermined plurality of command lines for transmitting and receiving control data and resource/application data to and from corresponding lines of the socket; wherein
the module includes means to selectively transmit and receive resource/application data over the plurality of transport stream lines.
The routing of resource/application data over the transport stream line may be selected on the basis of one or more of a number of a number of factors.
The receiver or conditional access device may have means to selectively transmit and receive resource/application data over the transport stream lines when the conditional access module is not required to process transport stream data.
In this way, when the conditional access module is not processing the transport stream and the transport stream would otherwise be merely passing through the conditional access module, the transport stream lines can be used for the resource/application data.
The receiver or conditional access module may also selectively transmit and receive resource/application data over the transport stream lines when the required data rate for the resource/application data exceeds the capacity of the command lines.
In this way, when an application or resource is being used which requires very high data rates, the transport stream lines may be used to allow full operation of that application/resource.
The receiver or conditional access module may also include means to selectively transmit and receive resource/application data in virtual channels of the transport stream which are not being processed by the conditional access module.
This is particularly useful where the conditional access module is only being used to process some of the time multiplexed virtual channels being transmitted as the transport stream over the transport stream lines. The conditional access module is still able to process the required virtual channels of the transport stream, but is able to take advantage of the present invention to transmit resource/application data of high data rate resources/applications in the remaining virtual channels over the transport stream lines.
Preferably, the receiver comprises means for rerouting transport stream data past the conditional access module when resource/application data is being transmitted over the transport lines.
The re-routing of data can be controlled in a number of ways. For instance, the user could merely control the receiver to use the transport stream lines for resource/application data, use of the transport lines might be chosen by the receiver automatically depending on its current load of operation or, where individual virtual channels are used selectively for resource/application data, the re-routing may be switched on the basis of the timing and usage of the multiplexed virtual channels of the transport stream.
Preferably to reduce the work load of the micro processor or resource manager in the receiver, the receiver further comprises means to route resource/application data received over the transport stream lines direct to the appropriate resource without intervention by the resource manager.
Preferably the digital video receiver is a DVB receiver, in which case the transport stream might be broadcast transport stream. However, the present invention can also be used in other systems with broadband inputs, for instance receiving high bandwidth transfer from sources such as an internet connection or a storage device such as DVD or DVCR.